1. Field of the Invention
The present invention relates to a position control method and a system, and more particularly relates to a position control method of an optical pickup head of an optical disc drive and a system thereof.
2. Description of Related Art
An optical disc has the advantages of reasonable price, portability, large storage capacity, easy data storage, long storage term, low cost, secure storage of data, and so on. Therefore, the optical disc has gradually replaced a conventional magnetic storage medium and becomes an indispensable optical storage medium in modern life. Because the optical disc is widely used, the optical disc player for accessing data in the optical disc becomes a common electronic product in modern life and also becomes standard equipment included by a computer.
FIG. 1 illustrates a schematic view of a conventional optical disc drive. Referring to FIG. 1, the optical disc drive 100 includes an optical pickup head 110, a lead screw 120, a spindle motor 130, a tray 140 and a step motor 150. The optical pickup head 110 is configured to access the data in the optical disc. The lead screw 120 is configured to drive the optical pickup head 110 moving along a radial direction of the optical disc. The tray 140 is configured to load and unload the optical disc. The spindle motor 130 is configured to support and rotate the optical disc. The step motor 150 is configured to rotate the lead screw 120. The “radial direction” mentioned above is the radial direction of the optical disc when the optical disc is disposed on the spindle motor 130.
When the optical disc drive is driving the optical pickup head 110 to move along the radial direction, the optical disc drive 100 transmits a step index to the step motor 150 so as to control the lead screw 120 to rotate and control the moving distance of the optical pickup head 110. In general, the step index represents the step number which the optical disc drive is moving the optical pickup head 110. The moving amount of each step number is about 6.25 μm. For example, when the step index is 500, the step motor 150 controls the lead screw 120 to rotate so the optical pickup head 110 moves 500 step numbers. That is to say, taking the moving amount of each step number is 6.25 μm for example, when the step index is 500, the optical pickup head 110 moves 3.125 mm. Therefore, the optical disc drive 100 may obtain the present radial position of the optical pickup head according to the step index so as to continuously control the optical pickup head 110 to move.
However, in the actual application conditions, during the process of the lead screw driving the optical pickup head to move, the driving error of the optical pickup head may occur due to sudden vibration or impact. Therefore, the radial position of the optical pickup head obtained according to the step index cannot accurately represent the radial position of the optical pickup head. Furthermore, the movement of the optical pickup head is mainly determined by the step index, so once the step index is different from the actual radial position of the optical pickup head, the optical disc drive can not accurately control the optical pickup head to move to the desired radial position.